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<jats:title>Abstract</jats:title> <jats:p>We compared high-resolution spectra of Betelgeuse observed before and during the Great Dimming. Atomic lines are shallow and broad during the Great Dimming presumably because of molecular veiling and increased macroturbulence, <jats:italic>ν</jats:italic> <jats:sub>macro</jats:sub> ≳ 23 km s<jats:sup>−1</jats:sup>. The best fit for TiO bands was found for the MARCS model atmosphere with <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> = 3500 K.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, I present the effects of single passing stars on planetary disks and explore the orbital modification of their components. I analyze the effects of passing stars and look for differences between flyby masses of 0.25 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, 0.5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, 0.75 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, and 1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Resultant eccentricities and inclinations of disk particles are fit to mathematical equations to estimate values for them as a function of their semimajor axes and the flyby mass.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The star 2MASS J07363415+6538548 (hereafter 2M0736) was previously classified as a possible symbiotic binary, a cataclysmic variable, an H <jats:sc>ii</jats:sc> region, a massive star cluster, a supernova remnant, or a high-mass X-ray binary. In the previous research, while analyzing disputable symbiotic candidates in our New Online Database of Symbiotic Variables, we employed multi-frequency photometric observations, and reclassified the object as an active K-type dwarf. Here, we analyze the low-resolution spectroscopy of 2M0736 to confirm its photometric classification and validate that our methods are able to provide comparable results with the optical spectroscopy. The obtained spectrum confirmed that 2M0736 is a K6 dwarf. The presence and strength of the H<jats:italic>α</jats:italic> emission line have verified that the object is very active.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Much of the information about the magnetic field in the Milky Way and other galaxies comes from measurements which are path integrals, such as Faraday rotation and the polarization of synchrotron radiation of cosmic ray electrons. The measurement made at the radio telescope results from contributions of volume elements along a long line of sight (LOS). A magnetic field measurement at a given spatial location is of much more physical significance. In this paper, I point out that H <jats:sc>ii</jats:sc> regions fortuitously offer such a “point” measurement, albeit of one component of the magnetic field, and averaged over the sightline through the H <jats:sc>ii</jats:sc> region. However, the LOS through an H <jats:sc>ii</jats:sc> region is much smaller (e.g., 30–50 pc) than one through the entire Galactic disk, and thus constitutes a “pseudo-local” measurement. I use published H <jats:sc>ii</jats:sc> region Faraday rotation measurements to provide a new constraint on the magnitude of magnetohydrodynamic turbulence in the Galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The goal of this Research Note is to provide the theoretical calculations of the limb-darkening coefficients and gravity-darkening coefficients (GDC) for the space mission <jats:sc>CHEOPS</jats:sc>. We use two stellar atmosphere models: <jats:sc>ATLAS</jats:sc> (plane-parallel) and <jats:sc>PHOENIX</jats:sc> with spherical symmetry covering a wide range of effective temperatures, local gravities, and hydrogen/metal. These grids cover 19 metallicities ranging from 10<jats:sup>−5</jats:sup> up to 10<jats:sup>+1</jats:sup> solar abundances, 0 ≤ log <jats:italic>g</jats:italic> ≤ 6.0 and 2300 K ≤ <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> ≤ 50,000 K. The specific intensity distribution was fitted using six approaches: linear, quadratic, square root, logarithmic, power-2, and a series with four terms. The calculations of the GDC were performed for both stellar atmosphere models adopting an improved formulation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using Gaia Early Data Release 3 (EDR3) parallaxes and Bayesian inference, we infer a parallax of the Westerlund 1 (Wd1) cluster. We find a parallax of 0.34 ± 0.05 mas corresponding to a distance of <jats:inline-formula> <jats:tex-math> <?CDATA ${2.8}_{-0.6}^{+0.7}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rnaasabdc2cieqn1.gif" xlink:type="simple" /> </jats:inline-formula> kpc. The new Gaia EDR3 distance is consistent with our previous result using Gaia Data Release 2 (DR2) parallaxes. This confirms that Wd1 is less massive and older than previously assumed. Compared to DR2, the EDR3 individual parallax uncertainties for each star decreased by 30%. However, the aggregate parallax uncertainty for the cluster remained the same. This suggests that the uncertainty is dominated by systematics, which is possibly due to crowding, motions within the cluster, or motions due to binary orbits.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I report a tentative (∼4<jats:italic>σ</jats:italic>) emission line at <jats:italic>ν</jats:italic> = 100.84 GHz from “COS-3mm-1,” a 3 mm selected galaxy reported by Williams et al. that is undetected at optical and near-infrared wavelengths. The line was found in the ALMA Science Archive after re-processing ALMA band 3 observations targeting a different source. Assuming the line corresponds to the CO(6 → 5) transition, this tentative detection implies a spectroscopic redshift of <jats:italic>z</jats:italic> = 5.857, in agreement with the galaxy’s redshift constraints from multi-wavelength photometry. This would make this object the highest redshift 3 mm selected galaxy and one of the highest redshift dusty star-forming galaxies known to-date. Here, I report the characteristics of this tentative detection and the physical properties that can be inferred assuming the line is real. Finally, I advocate for follow-up observations to corroborate this identification and to confirm the high-redshift nature of this optically-dark dusty star-forming galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The comparison of all unpublished archival IUE spectra of the bright spectroscopic binary <jats:italic>α</jats:italic> Draconis shows that the far-ultraviolet flux has remained constant over the 18 yr of the mission, except possibly for one spectrum which shows significantly less flux below 1800 Å. The Si <jats:sc>ii</jats:sc> lines undergo large radial velocity variations which are due to the orbital motion of <jats:italic>α</jats:italic> Draconis around the center of mass of the system. The far-UV energy distribution of <jats:italic>α</jats:italic> Draconis has more flux than that of Sirius A (<jats:italic>α</jats:italic> CMa) which reflects the weaker abundances of the metals in <jats:italic>α</jats:italic> Draconis compared to Sirius A.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report polarization properties for eight narrowband bursts from FRB 121102 that have been re-detected in a high-frequency (4–8 GHz) Breakthrough Listen observation with the Green Bank Telescope, originally taken on 2017 August 26. The bursts were found to exhibit nearly 100% linear polarization, Faraday rotation measures bordering 9.3 × 10<jats:sup>4</jats:sup> rad m<jats:sup>−2</jats:sup>, and stable polarization position angles, all of which agree with burst properties previously reported for FRB 121102 at the same epoch. We confirm that these detections are indeed physical bursts with limited spectral occupancies and further support the use of sub-banded search techniques in FRB detection.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the discovery of CWISE J203546.35–493611.0, a peculiar M8 companion to the M4.5 star APMPM J2036−4936 discovered through the citizen science project Backyard Worlds: Planet 9. Given CWISE J203546.35–493611.0's proper motion (<jats:italic>μ</jats:italic> <jats:sub> <jats:italic>α</jats:italic> </jats:sub>, <jats:italic>μ</jats:italic> <jats:sub> <jats:italic>δ</jats:italic> </jats:sub>) = (−126 ± 22, −478 ± 23) and angular separation of 342 from APMPM 2036−4936, we calculate a chance alignment probability of 1.15 × 10<jats:sup>−6</jats:sup>. Both stars in this system appear to be underluminous, and the spectrum obtained for CWISE J203546.35–493611.0 shows a triangular <jats:italic>H</jats:italic> band. Further study of this system is warranted to understand these peculiarities.</jats:p>